1. Field of the Invention
The present invention relates generally to a digital video recorder and, more particularly, to a method of adding a camera using a new protocol to a digital video recording system without interrupting a surveillance function.
2. Description of the Related Art
Recently, as Digital Video Recorders (DVRs) are becoming popular, a plurality of surveillance cameras are installed in an area where security is required, captures surveillance images, and transmits the captured image data to a DVR, which is at a remote location relative to the cameras, for recording in the DVR.
Furthermore, a recent surveillance camera includes a lens having a zoom function, so that it can magnify and photograph a distant object (tele-photographing) or can photograph a plurality of subject objects at one time (wide-angle photographing). Furthermore, the surveillance camera is mounted on a pan/tilter for rotating the camera in horizontal and vertical directions, so that it can photograph all portions of the area in which the surveillance camera is installed at various angles. The surveillance camera provided with such panning, tilting, and zoom functions is called a ‘Pan/Tilt/Zoom (PTZ) camera.’
FIG. 1 is a diagram showing an example of a connection between a plurality of PTZ cameras 1001 to 100k and a DVR 200.
Images captured using the plurality of PTZ cameras 1001 to 100k are transmitted to the DVR 200, which is at a remote location relative to the PTZ cameras, and are output to the monitor of the DVR or recorded on a storage medium.
Furthermore, the lateral and vertical rotation operations and zooming operations of each of the PTZ cameras 1001 to 100k are controlled in response to commands input by the operator of the DVR 200. In this case, control messages that correspond to the commands are transmitted to a corresponding camera. Cameras manufactured by different manufacturers may be used as the plurality of PTZ camera 1001 to 100k. In this case, the communication protocols differ according to respective manufacturers, so that different control messages must be used in accordance with respective targeted cameras to be controlled.
For example, as shown in FIG. 2, respective PTZ cameras manufactured by manufacturers A to D use intrinsic protocols (for example: A-protocol, B-protocol, C-protocol, D-protocol), messages, that is, packet data formats, each of which contains control commands, differ according to the respective protocols.
Generally, a main application, which is a file to be executed in a processor, is created by compiling and linking a source file, which is written in C language or the like, with the protocol header files of respective cameras.
That is, as shown in FIG. 3, an engineer who develops a DVR compiles and links an A-protocol header file ‘A_Protocol.h’ and a B-protocol header file ‘B_Protocol.h’ with a source file ‘Main_PTZ_Control.c’, and thus the main application, which is a program for performing the capturing and recording of a surveillance image and a camera control operation, is created.
FIGS. 4 and 5 are diagrams showing an A-protocol header file ‘A_Protocol.h,’ which is suitable for a protocol for a PTZ camera manufactured by manufacturer A, and a B-protocol header file ‘B_Protocol.h,’ which is suitable for a protocol for a PZT camera manufactured by manufacturer B, respectively. In the example of FIG. 4, the cameras of manufacturer A are controlled using an 8-byte command packet. In the example of FIG. 5, the cameras of manufacturer B are controlled using a 15-byte command packet.
However, when it is desired to add a PTZ camera using a new protocol to a DVR system, the DVR development engineer must interrupt the main application, which is a currently running program, updates the main application so as to include a header file for the new protocol as described above with reference to FIG. 3, and reboot the system to apply the updated main application thereto. In this case, a problem occurs in that the surveillance function is interrupted.